Gyratory sifter



June 20, 1950 P. M. THOMPSON GYRATQRY SIFTER 5 Sheets-Sheet 1 Filed Nov. 10, 1944 AT om/Eys June 20, 1950 P. M. THOMPSON ,88

GYRATORY SIFTER Filed Nov. 10, 1944 I 5 Sheets-Sheet 2 IN VEN TOR.

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BY 9 "m ATTORNEYS June 20, 1950 P. M. THOMPSON GYRATORY SIFTER 5 Sheets-Sheet 3 Filed Nov. 10, 1944 ATTORNEY;

P. M. THOMPSON GYRATORY SIFTER June 20, 1950 Filed Nov. 10, 1944 5 Sheets-Sheet 4 ATTORNEYS June 20, 1950 P. M. THOMPSON I 2,511,885

cm'ronv SIFTER Filed Nov. 10, 1944 s Sheets-Sheet 5 A TTOP/VEYS Patented June 20 1950 UNITED STATES PATENT OFFICE GYRATORY SIFTER Application November 10, 1944, Serial No. 562,753

6 Claims. (Cl. 209332) This invention relates to a high speed sifter and more particularly to such a sitter which is suspended from reeds and which includes an eccentrically weighted rotary shaker for imparting a rotary movement in a horizontal plane to describe perfect circles of adjustable diameter or amplitude. Features of the invention can be advantageously utilized in sitters other than the particular type shown, however.

One of the principal objects of the invention is to provide sucha sifter which operates upon large quantities of material and will sift them at a high rate of speed. To this end features of the invention reside in the elimination of escaping vibrations which disturb the balance of the sifter and which are greatly magnified at high speed and heretofore have prevented the operation of a sifter at the high speed achieved by the present invention.

Another object of the invention is to provide such a large capacity sifter in which the sifter frame is gyrated in a horizontal plane to describe perfect circles and in which the amplitude or diameter of such circles can be readily adjusted to obtain the desired effect.

Another object isto provide a sitter which will operate at high speed without undue strain on any of the parts, particularly such strains as are liable to cause breakage.

Another object is to provide a belt tightener which is adjustable while the sifter is in operation and which can be made accessible from either side of the sitter.

Another aim is to provide an adjustable belt drive in which the drive can be from above or below and in either direction and in which the tightening is alwayseffected on the loose side of the belt.

Another object is to provide an eccentri'cally weighted shaker in which the return springs for the eccentric weights are of such form as not to ride up on one another when the springs bottom and in which the sliding rods which carry the eccentric weights are not impeded intheir sliding movement by dust or dirt settling thereon.

Other objects and advantages will appear from the following description and drawings in which:

Fig. 1 is a side elevational view of a high speed sitter embodying the present invention.

Fig. 2 is an end elcvational view.

Fig. 3 is a top plan view, showing the sup porting reeds insection.

Fl'g. 4a is a vertical sectional View taken on line ti', Fig. 3 and showing some of the screens in elevation.

Fig. 5 is an enlarged horizontal sectional View, taken on line 5-5, Fig. 2.

Figs. 6, '7 and 8'- are fragmentary, vertical sectional views, taken on the correspondingly numbered lines on Fig. 5. i

Fig. 9 is anenlarged fragmentary horizontal section, similar to Fig. 3, and showing parts of the shaker mechanism in section.

Fig. 10 is a fragmentary sectional view taken on line Ill-4t, Fig. 9.

Fig. 11 is a fragmentary View similar to Fig. l and showing one top frame released and lifted by its supporting springs to render accessible the screen frames of the corresponding stack.

Fig. 12 is an enlarged fragmentary vertical sectional view, taken on line Il -l2, Fig. 1.

Fig. 13 is a view similar to Fig. 12 and showing a modified form of belt tightener.

The body of the high speed sifter embodying the present invention is generally of rectangular boxlike form and is shown as carrying a stack of screens at its Opposite ends, although it will be understood that four stacks of screens could be provided, two at each end,- to double the capacity of the sifter. Since the body is of identical construction at its opposite ends, the same reference numerals will be used to designate similar parts at each end.

The main supporting frame for the sitter comprises a pair of horizontal side channel beams 29 which are arranged on opposite sides of the sifter and which are arranged in a horizontal plane intersecting the center of gravity of the sifter. The channels of these channel beams 20 are shown as facing outwardly and at the center of the sifter these side channel beams are shown as rigidly connected by a pair of horizontally spaced transverse channel beams 2|, the ends of which can be welded to the side channel beams 20 and reinforced by gussets 22 which serve to hold the channel beams 2|] and 2| in rectangular relation. A pair of horizontal channel beams 23 are arranged centrally of the sitter to extend fore-and-aft and are secured at their ends, by bolts 24 or in any suitable manner, to the upper and lower sides of the transverse channel beams To support this main frame for gyratory circular movement in a horizontal plane, each end of each of the main longitudinal side channel news 2%] is supported by a plurality of wooden reeds 25. The upper ends of each group of these wooden reeds 25 is shown as anchored in a support it secured to the ceiling framework of the building in which the sifter is housed and the lower end of each group of reeds 25 is secured by a block and clamping plates 28 to the outer face of the corresponding longitudinal side channel beam 28 by screws 29 or in any other suitable manner. An important feature of the invention, however, resides in the connection between the reeds 25 and the main longitudinal side beams 28 of the frame being at places which lie in a plane intersecting the center of gravity of the snter, this being an important feature in securmg perfect circular movement of the sifter without escaping vibrations and in enabling the sifter forming the subject of the present invention to be gyrated at a much higher speed than has been possible heretofore.

To gyrate the main frame, in a horizontal plane to traverse such perfect circles, a shaker mechanism is provided which is preferably constructed as follows:

A vertical shaft 38 is journaled in the longitudinal central channel beams 23 by a thrust bearing 3| carried by the upper longitudinal central channel beam 23 and a bearing 32 carried by the companion lower central longitudinal channel beam 23. This lower bearing 32 need not be a thrust bearing since in operation the shaft 38 floats so that the upper bearing3l is made in the form of a thrust bearing to support the shaft 38 when the sifter is at rest. It is important, however, that the shaft 38 intersect the center of gravity of the sifter. At this point of intersection of the shaft 38 and the center of gravity of the sifter, a drive pulley 33 is fast to the shaft 39, this pulley thereby being disposed in the center of gravity of the sifter. A further important feature. of the invention resides in the fact that this drive pulley 33 is arranged between the two longitudinal central channel beams 23 of the sifter frame, as shown in Fig. 4. This pulley 33 has a lower flange 34 to support a drive belt 35, the two stretches of which belt can pass horizontally outward from either side of the sifter through a pair of openings 36 provided in each of the main longitudinal side channel beams 28 for this purpose.

Outside of these openings 36, idler pulleys 36 and. 39 are mounted on the corresponding main longitudinal side beam 28 and from these pulleys the corresponding stretches of the belt 35 are shown as passing under pulleys 48 carried by a bed or support 4| and thence passing around a drive pulley 42 on the shaft of a motor 43. It will particularly be noted that while the stretches of the belt 35 are shown as extending downwardly to the pulleys 48, they could with equal facility, eX- tend upwardly to overhead pulleys, this flexibility in installation and drive being one of the advantages of the invention. Further, it will be seen that the belt 35 can pass out through the openings 36 at either side of the sifter, this further facilitating the installation of the sifter in that the drive for the sifter can be from either side and from above or below.

The pulley 39 on the tight side of the belt 35 can be secured to the corresponding main longitudinal side beam 28 of the frame by a bearing bracket 65 of any suitable character but the pulley 38 on the loose side of the belt 35 is shown as being adjustable to permit of tightening the belt, the ability to tighten the belt while the sifter is in operation being an important feature 01 the invention.

For this purpose, as best shown in Fig. 12, the pulley 36 is shown as rotatably mounted between the arms of a yoke 35, the upper end of this yoke being pivoted to a bracket 48 which s in turn secured to the top flange of the adjacent main longitudinal side channel beam 28. To the lower end of one arm of this yoke 46 is pivotally secured one end of a horizontal adjusting rod 49 which extends horizontally across to the other side of the sifter and through an opening provided in a bracket 50 secured to the opposite main longitudinal side channel beam 28. The free end of the adjusting rod 49 is threaded and works in a hand adjusting nut 5| which is rotatably mounted, but held against axial movement by the bracket 50. It will be seen that turning the nut 5| by hand serves to move the adjusting rod 49 axially thereby to swing the yoke 46 and it pulley 38 inwardly or outwardly, this, in turn, tightening or loosening the slack stretch of the belt 35 which passes over this pulley 38. This adjustment can be made while the sifter is in operation. The brackets 48 and 45 are preferably interchangeable in position so that the pulley 38 can always be located to contact the slack side of the belt 35.

If it is found desirable to have the belt tightener operable from the side of the sifter from which the stretches of the belt 35 extend, the modified form of belt tightener shown in Fig. 13 can be employed. In this modified form of belt tightener, one depending arm of the yoke 43 is pivotally connected with a short screw '53 which is arranged in axially opposed relation to a short screw 54 fixed to a bracket 55 secured to the adjacent main longitudinal side beam 28. The screws 53 and 54 are reversely threaded and are connected by a manually operable turnbuckle nut 56. It will be seen that by turning this turnbuckle nut 56, the yoke 46 and pulley 38 will be swung inwardly or outwardly to tighten or loosen the belt 35 in the same manner as with the form of belt tightener shown in Figs. 1, 2, 3, 5 and 12.

The shaft 30 is eccentrically weighted at its opposite ends to cause the frame, suspended by the reeds 25, to gyrate in a horizontal plane in perfect circles. As these eccentric weights are identical in construction, a description of one will be deemed to apply to both.

The numeral 58 represents an H-shaped rectangular head or block fast to the corresponding end of the shaft 38 and in the arms of which a pair of horizontal parallel rods 59 are slidably mounted. To the corresponding ends of these rods 59 is secured a D-shaped weight 60, the fiat side of this D-shaped weight bearing against the corresponding face of the supporting block or head 58 so that this weight is always eccentric to the axis of rotation of the shaft 38. The rods 59 project from the opposite side of the supporting block or head 58 and have threaded extremities which receive an adjusting nut BI and a lock nut 62. Interposed between each adjusting nut 6| and the supporting block or head 58 is a helical compression spring 63, this spring surrounding the corresponding rod 59 and the metal or wire forming its convolutions being rectangular in cross section. An important feature of the invention resides in the provision of a spiral groove 64 in each of the rods 59.

The D-shaped weights 68 are arranged eccentric to the axis of the shaft 30 and hence when the motor 43 is started and the weights 68 rotated, these weights tend to move radially outward, their rods 59 sliding in the supporting block or head 58 against the resistance of the square or rectangular springs 63. The further these weights swing out, the greater the orbit of oscillation of the sifter frame, the maximum outward position of the weights: 58 being determinedvby the. spe'edcf rotation of the. shaft 30- and the degree or resistance of the springs 63. Assuming the motor 43 to have a. constant speed, itxwill be seen that the size of thecirclest described by the frame of the sifter will be determined by the adjustment. or" the nuts 6|. which determines the effective pressureexerted by thesprl-ngs 63:. A feature of the shaking. mechanism resides in. the use of springs 63, the metal or wire forming the convolutions of Whicharefl'at sided or rectangul'ar in cross section With such springs, as the centrifugal force of! the. weights 68 tends to bottom the coilsv of the springs, there isno tendency for these coil'si to ride up on'each other as: would be: the case if the metal'or wire of: these coils were round in cross section. Further; by the provision ofthe spiral groove Mineach rod 59, there is no tendency for these rods to foul as would be the case if these spiral grooves were not provided. Any dust settling on the rods. 59 is sheared off as the successive portions or the spiral grooves enter the supporting block 58. instead of clogging: theslideways therein and impeding the. free sliding movement of, the rods 59.

At spacedintervals along each of the main longitudinal side channel beams 2d of the sifter frame, depending rods 66 extend upwardly through the flanges: of beam 20. and are. secured to nuts 68 supported on the upper flange of this beam. These rods 66 extend through the side angle bars 69- of a. supporting platform frame Ill composed of these side angle. barsv 69, end traverse angle bars 'II" connecting the ends of the side bars 68', and intermediate transverse angle bars T2 connecting the intermediate parts of the side bars 69 at places directly. below the transverse'channel beams 2I of" the main frame of the sifter. The platform frame, composed of the angle bars 69, H and I2 is supported by nuts 13 at the lower ends of the vertical rods 66.

At each end of the sifter a rectangular horizontal platform M is secured to the frame- It, each of these platforms being secured at its edges in any suitable manner, to the undersides of the adjacent rectangle of the angle bars. 6?), H and 12 of this platform frame. Each 01 these platforms is provided with spouts 15 through which the sifted material is discharged in separate streams and each platform [4 carries a stack of screens indicated generally at it.

The screens of each stack can be of any suitable construction to sift, bolt, separate, screen or grade the material into difierent sizes. Each of these screens is shown as including an inner wooden frame 8U of square or rectangular form which is shown as provided on one of its. longitudinal sides with a vertical.throughs passage 82 which may be divided into sections by a partition 83 and provided on its opposite longitudinal sides with vertical inner throughs channels I82 which may be divided into sections by a partition I83. At one of its transverse sides, the inner screen frame is shown as provided with a vertical overs channel or passage M which extends across the entire Width of-this frame and may be divided into one or more sections by a partition 85. The opposite transverse end of the inner screen frame is closed or unprovided with any vertical passage but the entire screen frame structure as above described is shown as enclosed by an outer rectangular frame 8% of the same height and connected therewith by corner blocks 88.

The-innerrscreen frame carries. a pairv of central cross bars '90 which. are parallel with. the sides; of the inner frame and hence cross each other at the center of theframe and divide the frame, into fourequal square. or rectangular screening areas. Allot these areas are covered bya, screen of bolting or; sifting cloth 9 I, this cloth being usually made of fine mesh woven. silk, although of." course, other. materials: could. be used. This bolting or screening cloth is secured at its glges to the: side bars of the inner screen frame Below the bolting screen a cleaner carrier 92 is mounted on the inner screen frame 80, thi cleaner carrier preferably consisting of. a grate of coarsely woven wires. upon whichthe screen cleaners; not showm are loosely supported; for

;cleaning the bolting'screen. cloth Bl from its und'crside. Below theclieanercarrier 92, a plate or sheet-=83 of sheet metal can be arranged to enclose the bottom of the inner screen, frame 80, this plate receiving the throughs and. directing them into one or the other of the throughs passages. or channels 82, I82 as determined by the inclination of this plate. and the side at the inner frame 88' leftopen abovethis plate- The various throughs and. overs passages oi the several screens .16 are arranged to deliverthe segregated material .to theproper spouts l5 in the platform 14 on which each stack of the screen frames I8 rests.

The top of each stack of the screens I5 is covered by a. rectangularheader which has side walls 96 engaging the outer rectangular frame 86 of the uppermost, screen and a top wall 98 provided with an inlet. spout 99 through which the materials: to be screened are admitted and deposited on the uppermost screen 16. Each stack. of the screens I6, together with its header 95', is securely clamped to the sifter frame by means which are preferably constructed as follows:

At the center of the sitter each of the two corners of each stack of screens It? is embraced by a vertical angle bar I00, each of these angle bars fitting into the corresponding corner between the main longitudinal channel beams 22 and the transverse channel beams 2| of the main. frame of the sitter, as best shown in Fig. 5. Similarly the other two corners of each stack of screens 16 are each embraced by a vertical angle bar IIlI, these angle bars I ll! being arranged inside of the main longitudinal channe beams 20 and the outer members 69 and 1| of the platform frame -'I0 To the lower end of each of these vertical angle bars I00, IllI is fixed a laterally outward projecting pin I02 which fits into a jaw I03 on top of the corresponding side bar 69 of the platform frame l0, these jaws opening horizontally and fore-and-aft of the sifter and the jaws for each stack of screens opening in opposite directions, as best shown in Fig. 4.

Each of the corner angle bars I 00, IGI is provided near its lower end with an outwardly projecting lug I04, these lugs projecting fore-and-att of the sifter and being" provided on their upper sides with a groove to receive a tie rod I85. Each tie rod is provided with a head at one end engaging one lug I04 and is threaded at its opposite: end to receive a wing nut H36, which bears against the adjacent lug Ill-d of the adjacent corner angle bar I08 or IiJ-I. It will therefore be seen that tighten-ingthe wing nuts Hi5 draws the lower ends of the corresponding pair of vertical angle bars 00 and lu l together to securely clamp the lower ends of the stacks of screens 15- therebe tween. Similarly each of the corner angle bars 100,- IN isprovided near its upper end with an outwardly projecting lug I08, these lugs projecting fore-and-aft of the sifter and being apertured to receive a tie rod I09. Each tie rod I is provided with a head at one end and is threaded at its opposite end to receive a wing nut I I0, which bears against the adjacent lug I06 of the adjacent corner angle bar I00 or IOI. t will therefore be seen that tightening the wing nuts IIO draws the upper ends of the corresponding pair of vertical angle bars I00 and IOI together to securely clamp the upper ends of the stacks of screens I6 therebetween.

To each end of each of the main longitudinal side beams 20 of the main frame of the sifter, is pivotally secured a clamping plate II which is L-shaped in horizontal section. For this purpose each of these L-shaped clamping plates H5 is provided with a pair of Vertically spaced ears I I6 each of which is secured by a vertical pivot bolt II8 to the corresponding flange of the adjacent main longitudinal side channel beam of the main frame of the sifter. As best shown in Fig. 5 these L-shaped clamping plates II5 are swingable to embrace the corners of the vertical angle bars IM and each is provided with an apertured ear II9 which projects longitudinally outward from the corresponding end of the sifter and the pair of these ears I I0 at each end of the sifter receiving a rod I20 which is threaded at its opposite ends. On each threaded end of each of these rods is a threaded hand wheel IZI, the hubs of which bear against the sides of the ears IIO so that upon tightening these hand Wheels the L- shaped clamping plates II5 are drawn together and into engagement with the vertical angle bars IOI.

To clamp each stack of screens 86 down upon its platform I4, each stack is capped or surmounted by a top frame indicated generally at I25, automatically lifting these top frames I being effected when the wing nuts which fasten them down are released. This automatic elevation of these top frames makes it unnecessary for the operator to climb up and lift them down in taking out the stacks of screens I6, the selflifting feature automatically lifting them free from the stack.

Each top frame I25 is made of angle irons connected to form a rectangle which fits over the upper header 35 of each stack of screens I6, as :best shown in Figs. 3 and 4. At each side this top frame is provided with a @pair of slotted ears I26 through each of which a vertical rod I28 extends. The lower end of each of these rods I28 is threaded and screws into the corresponding nut 68, these nuts 68 supporting the rods 66 as previously described. Above the nut 68, a collar I29 is fixed to each rod I28 and a helical compression spring I30 is arranged around each rod I26 and is interposed between each collar I29 and the corresponding ear I26 of the top frame I25. The springs I30 are of sufficient strength that, when each top frame I25 is released, they lift this top frame to the position shown in Fig. 11 in which position the stack of screens 76 are directly accessible for removal. The lifting movement of these springs I30 is limited by a stop collar I3I at the upper end of each rod I28.

The top frames are drawn down to clamp the stack of screens I6 against the platform I4 by wing nuts. For this purpose the side angle bars of the top frame I25 are extended longitudinally fore-and-aft of the sifter to provide a pair of longitudinally slotted ears I35 at the inner cor-.- ners of the top frame and a pair of longitudinally slotted ears I36 at the outer corners of the top frame. A swing bolt I38 is pivoted to each ear I08 of the inner vertical angle bars I00 and swings into the slot of the corresponding ear I35. Each swing bolt I38 is provided with a wing nut I39 and it will be seen that upon tightening these wing nuts I39, the inner ends of the top frames I25 are drawn downwardly to firmly clamp the rear of the stacks of screens I6 downwardly against their platforms I4. To similarly clamp down the outer corners of each top frame I25, a cam I40 is rotatably mounted on each end of each horizontal rod I20, this cam I40 havin a cam face I4I which engages the corresponding face of the adjacent vertical angle bar IOI when the cam member is rotated clock- Wise as viewed in Fig. 6. This rotation of this cam member thereby serves to provide horizontal end clamping pressure to urge the stack of screens I6 toward the center of the sifter. Each cam I40 also serves as the anchorage for the lower end of a rod I42 which extends upwardly through the corresponding slotted ear I36. The upper end of each of these rods I42 is threaded to receive a wing nut I43 which bears against the top of the corresponding ear I36. It will therefore be seen that screwing down the wing nuts I43 not only tightens down the outer ends of the top frames I25 but also rotates the cams I40 clockwise, as viewed in Fig. 6, to force the corner angle bars IOI horizontally toward the center of the sifter to provide a horizontally acting end clamp for each stack of screens I6.

The clamping of each stack of screens I6 is completed by master clamps which urge the inner vertical angle bars I00 of the stacks toward each other. For this purpose a plate I50 is bolted to the inner face of each of the transverse channel beams 2| of the main frame of the sifter. Each of these plates I50 has a threaded stud I5I which projects out through a hole provided in the corresponding main longitudinal side channel beam 20 of the main frame of the sifter. Each stud I5I extends through a clamping plate I52 housed in the channel of the corresponding channel beam 20 of the main frame and each stud is provided with a nut I54. The opposed ends of the clamping plates I52 are provided with laterally extending lugs I55 which fulcrum against the outer faces of the channel beams 20 of the main frame and the opposite end of each clampin plate I52 carries two pins I56 which extend through holes in the channel beam 20 of the main frame to engage the side of the corresponding corner angle bar I00 of the stack of screens I6. It will be seen that tightenin the nuts I54 draws the clamping plates I52 inwardly and, through their pins I56, forces the inner vertical corner angle bars I00 of the stacks toward each other to firmly clamp the stacks of screens I6. It will further be seen that the strain on the main frame in providing this master clamping action is directly lengthwise of the transverse channel beams 2I of the main frame thereby to avoid all danger of crystallizing the main frame in providing such clamping action. The avoidance of strain upon the main frame in clamping the stacks of screens I6 in position is of paramount importance in providing a heavy duty high speed sifter.

The sides of the sifter can be enclosed by upper and lower side plates I58 and I59 which can be secured in position in any suitable manner and the main longitudinal side channel beams 20 of the main frame canlikewise be provided with coverplates liill. These enclosing plates are provided with apertures for the various rods and other parts of the sifter.

In the operation of the sifter, at high speed it is of paramount importance that the body of the sifter be gyrated in a horizontal plane to describe perfect circles and without escaping vibrations, the presence of such escaping vibrations preventing the high speed operation of a sifter ofthis character as heretofore constructed. To avoid escaping vibrations, it is important that the anchorages '28 for the frame on the reeds 25 be in a plane intersecting the center of gravity of the sifter. It is further important that the vertical shaft 39, which is journaled in the main frame, intersect this center of gravity and that its pulley 33 be located at this center of gravity and between the two central longitudinal beams 23 of the main frame. When this pulley 33 is driven by the belt 35 the weights 60 eccentrically carried at the upper and lower ends of the vertical shaft 3i! serve to gyrate the frame to traverse perfect circles and without escaping vibrations.

As the vertical shaft 30 picks up in speed, the two weights @St move radially outward under the increasing centrifugal force, this movement being permitted by the .rods 59 which are slidingly mounted in the head or block 58 fast to the shaft at. This movement is resisted by the helical compression springs 53 around these rods, these springs also returning each weight 60 to engagement with the head or .block 58 so that in starting the sifter a minimum throw is provided by these weights. To prevent the coils of these springs from riding up on one another when subjected to a bottoming load, the metal forming the coils of these springs is flatsided or rectangular in cross section. The rods 59- are also provided with the spiral grooves '64, the dust collecting on the rods entering these grooves and being removed as a mass so as not to interfere with the free sliding movement of the rods. It will also be seen that the adjustment of the nuts Bl determines the size of the circle described by the frame, these nuts controlling the restrainin pressure exerted by the springs 63.

From the pulley 33, the horizontal stretches of the belt 35 can pass out through the slots 36 provided in each main longitudinal side frame beam 2t, so that power can be applied from either side of the sifter. These stretches then pass over the pulleys 38 and 39 from which the belt can be directed either upwardly or downwardly (as shown) to the power source. To permit of tightening the belt 35, its slack stretch passes over the pulley 33 which is mounted on the pivoted yoke 45. Upon adjusting the nut 5| shown in Fig. 12 or the turnbuckle nut 56 shown in Fig. 13, it will be seen that the yoke 46 is swung toward or from the corresponding main side longitudinal beam 2B to adjust the tension on the belt 35.

It will also be noted that the stacks of screens F6 are clamped together as a mass separate from the main frame and that each stack or mass of screens is clamped to the main frame in such manner as to avoid irregular stresses on the main frame. It has been found that the main frame soon breaks down, due to crystallization when such irregular stresses are present. In particular each stack or mass of screens 16 is principally clamped to the main frame by the master clamping plates I52 which fulcrum on the outer faces of the main. longitudinal side beams 20 at I55 and have pins ['56 which project through holes in the side beams 28 to engage and clamp against the inner corner angle bars of the stacks of screen frames. It will be observed that these master clamping plates I52 are tightened from the studs l5! which project directly out from the ends of the transverse channel beams 21 of the main frame. The stress of this clamping is therefore borne almost entirely by endwise tension against the transverse channel beams 2| of the main frame and hence without undesirable strain.

The stacks are supported on the springs l30so that these top frames are automatically lifted when the clamping wing nuts I39 and I43 are removed. It will be noted that this self-lifting of the top frames is provided by the simple expedient of screwing upstanding rods I28 in the same nuts E58 which carry the depending rods 66 which support the stack of screens, and threading helical compression springs I33 on these rods, these springs engaging ears provided on the top frames.

From the foregoing it will be seen that the present invention provides a suspended sifter which can be gyrated at high speed to describe perfect circles in a horizontal plane and without escaping vibrations.

I claim as my invention:

1. In a high speed sifter having a suspended frame carrying screens, means for moving said frame in a horizontal plane to describe circles, comprising a vertical shaft journaled in said frame and intersecting the center of gravity of said frame, means fast to said shaft at said center of gravity and driving said shaft about its axis, and eccentric weights fastened :to the respective ends of said shaft to rotate about said axis and arranged between the 'top and bottom of the sifter.

2. In a high speed sifter having a suspended frame carrying screens, means for moving said frame in a horizontal plane to describe circles, comprising a vertical shaft journaled in said frame and intersecting the center of gravity of said frame, a pulley fast to said shaft at said center of gravity, a belt driving said pulley, eccentric weights at the ends of said shaft and arranged between the top and bottom of the sifter, and means securing each of said weights to the corresponding end of said shaft but permitting radial movement with respect thereto.

3. In a high speed sifter, a frame carrying screens and including spaced main longitudinal horizontal side beams, horizontally spaced transverse beams connecting said side beams near the center of the frame and vertically spaced longitudinal central beams connecting said transverse beams at the center of the frame, means suspending said frame, and means for moving said frame in a horizontal plane to describe circles, comprising a vertical shaft journaled in said longitudinal central beams and intersecting the center of gravity of said frame, means fast to said shaft between said longitudinal central beams and at said center of gravity and driving said shaft, and eccentric weights at the respective ends of said shaft and each arranged between the corresponding longitudinal central beam and the corresponding vertical extremity of each screen frame, and means securing each of said weights to the corresponding end of said shaft but permitting radial movement with respect thereto.

4. In a h h speed ifter, a frame carrying '11 screens and including spaced main longitudinal horizontal side beams, horizontally spaced transverse beams connecting said side beams near the center of the frame and vertically spaced 1ongitudinal' central beams connecting said transverse beams at the center of the frame, means suspending said frame, and means for moving said frame in a horizontal plane to describe circles, comprising a vertical shaft journaled in said longitudinal central beams and intersecting the center of gravity of said frame, a pulley fast to said shaft between said longitudinal central beams and at said center of gravity, a belt driving said pulley, and eccentric weights at the ends of said shaft within the confines of said screen frame and above and below, respectively, said longitudinal central beams and rotating with said shaft.

5. In a high speed sifter, a horizontal frame, comprising horizontally spaced main longitudinal side beams, horizontally spaced transverse beams connecting said side beams near the center of the frame and vertically spaced longitudinal central beams connecting said transverse beams, means for supporting an uninterrupted stack of sieves between the corresponding outer ends of said side beams with said side beams embracing the central portions of said stacks, means suspending said frame, comprising a reed supported at its upper end over each end of each of said side beams and extending downwardly and means securing the lower end of each reed to the corresponding outer end of said side beam, and means for moving said frame in a horizontal plane to describe circles, comprising a vertical shaft journaled in said longitudinal central beams, means fast to said shaft between said longitudinal central beams and driving said shaft about its axis, and eccentric weights fastened to said shaft above and below respectively of said longitudinal central beams, each of said stacks extending a substantial distance above and below said eccentric weights.

6. In a high speed sifter, a frame carrying screens, means forsuspending said'frame, comprising a plurality of-vertical reeds supported at their upper ends above said frame and extending downwardly to adjacent'difierent portions of said frame and means securing thelower ends of said reeds to said frame in a horizontal plane arranged approximately at the center of said frame, and means for moving said frame in said plane to describe circles, comprising a vertical shaft journaled centrally in said frame and intersecting said plane, means fast to said shaft in said plane and driving said shaft about its axis, and eccentric weights fastened to the respective ends of said shaft immediately above and below said plane and within the confines of said screen frame to rotate about said axis.

PEYTON M. THOMPSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 726,073 Konegan Apr. 21, 1903 732,019 Wolf June 23, 1903 952,565 Fraser Mar. 22, 1910 1,100,149 Prokop June 16, 1914 1 1,192,501- Combs July 25, 1916 1,403,923 Thompson Jan. 17, 1922 1,434,252 Neal et al Oct. 31, 1922 1,782,561 Boldizar Nov. 25, 1930 2,020,013 Bailey Nov. 5, 1935 2,097,347 Shaler Oct. 26, 1937 2,267,153 Holland Dec. 23, 1941 FOREIGN PATENTS Number Country Date 108,924 Switzerland 1 Feb. 16, 1925 658,636 France Jan. 26, 1929 

